Intel Core i5 661 Dual Core LGA 1156 Processor Review

The new 32nm Core i5 600 series processors would not be possible without the significant changes made with the first generation of LGA 1156 CPUs. So first, let’s review the architecture changes that we find in the earlier LGA 1156 processors. They have a dual-channel onboard memory controller, and a PCI-E x16 interface for communications with the graphics card, both of these functions were traditionally done in the Northbridge. In addition, a modified PCI-E x 4 interface with the I/O hub allows for a much lower speed IOH and it was taken off of the NB and put on the Southbridge. These changes allowed for the complete elimination of the Northbridge.

Also, Hyperthreading finally came of age and the LGA 1156 Core i7s had four real threads and four virtual threads, creating the effect of eight cores, which was a carryover from the LGA 1366 Core i7s. The earlier quad-core Core i5 750 did not have Hyperthreading, which was the main difference between the LGA 1156 i7 and i5.

Finally, Intel Turbo Boost was another creation carried over from the LGA 1366 series. Using Intel Enhanced SpeedStep, the processor goes to a lowered power state when idle by lowering the CPU multiplier. When the processor is under load, it actually gets overclocked, the CPU multiplier can increase beyond stock clock. This can happen on one or both cores. So the processor automatically underclocks and overclocks according to workload.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

The new Clarkdale CPUs are built with the 32nm manufacturing process, so they are smaller and run cooler than the earlier models. Intel started work on their US based 32nm factory early last year and they are already in operation. Rather than placing 4 cores on the die, Intel decided to go with a pair, leaving plenty of extra room on the die. Hyperthreading was added giving the effect of a quad-core processor, theoretically giving the new i5s the processing power of the earlier Core i5 750.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

Already having a PCI-E interface for communication with the graphics card, combined with having all of that extra room on the CPU die, I guess it just seemed natural to place a VGA in the open space. The Core i5 600 series’ IGP (Integrated Graphics Platform) is called the “Intel Graphics Media Accelerator HD”. This was derived from the GMA X4500 HD, the VGA found on the Intel G45 chipset. This has been beefed up for use with the Clarkdale processors, with shaders being increased from 10 to 12, memory support from up to 768MB to up to 1.7GB, and a bandwidth of 21.2GB/s (theoretical) which is around 25% greater than the X4500HD. Intel claims that the Core i5 600 series’ graphics will operate about 1.5 times faster than the integrated graphics on the G45. By the way, the IGMA HD on the Core i5 600 series is built in the 45nm process.

Also to note, the processor’s memory controller is also located within the IGMA HD.

Intel Core i5 661 Dual Core LGA 1156 Processor Intel Core i5 661 Dual Core LGA 1156 Processor

I realize that I’ve thrown a lot of information at you in the preceding few paragraphs, and you probably haven’t thought about the fact that though the existing Intel P55 chipset is the same LGA 1156, there are no provisions to use the Core i5 600’s onboard graphics. Intel has introduced three new chipsets to solve this, the H55 Express, the H57 Express, and the Q57 Express. We can assume that the H55 is a modified P55, the latter two are new chipsets. At the time of this writing, motherboards of all three chipsets are available.

So what about the P55 motherboards? The Intel Core i5 600 series will operate on P55 boards, just without the graphics support. Performance should be somewhat less compared to the i5 750, but we’ll see what the performance looks like later.